By doing so, she started a case that evolved "the natural way where someone is truly indignant about what happened to them," says Kaplan, a corporate lawyer with Paul Weiss.

Windsor began to feel the effects of DOMA when her partner Thea Spyer died in 2007.

Because the IRS didn't recognize their marriage performed in Canada, Windsor had to pay $363,000 in taxes on Spyer's estate that a straight spouse wouldn't have had to pay.

On March 27, Kaplan will argue that the tax bill and the law that allowed it are unfair before the Supreme Court, a day after it hears a case involving California's anti-gay marriage law Proposition 8.

Windsor initially asked not-for-profit legal groups to argue her case, but they said it wasn't the right time, according to Kaplan. Kaplan felt differently when she and Windsor were introduced by a mutual friend.

"The minute I heard the facts of the case, it took me about three seconds to decide that it was absolutely the right case to bring," says Kaplan, whose firm took the case on free of charge.

Windsor's case involved a very specific injury that everyone can relate to: an unfair tax bill.

"Every American gets in their gut what it means to have to pay a huge tax bill where you wouldn't have to pay the same tax bill if you weren't gay. Everyone understands what that means," Kaplan says.

Windsor's age also makes her an ideal candidate to bring down DOMA. It will be easier to strike down DOMA if the Supreme Court rules the law must face "heightened scrutiny" because it impacts people who've endured a history of discrimination.

For Windsor, discrimination isn't "theoretical," Kaplan tells us. Windsor's brief to the Supreme Court chronicled her own "life in the shadows," as Lyle Denniston of SCOTUSBlog reported.

When she fell in love with Spyer nearly 50 years ago, the brief noted, it was a “a time when lesbians and gay men risked losing their families, friends, and livelihoods if their sexual orientation became known."

If the Supreme Court strikes down DOMA, same-sex couples in the nine states where gay marriage is legal will know the federal government now recognizes the legitimacy of their relationships. They'll also get benefits they didn't get before. If one spouse dies, the other could take his or her social security if it's more money. They won't have to pay estate taxes.

The repeal of DOMA could, in fact, have a very real impact on a lot of people. But one woman's story could help convince the Supreme Court to do away with the law.

Throughout preparations for the case, Kaplan, the lawyer who's telling that story, has kept a post-it note on her desk that's a variation of Bill Clinton's successful 1992 campaign phrase: